1590s, from Greek Prōteus, sea god (son of Oceanus and Tethys) who could change his form; his name is literally "first," from prōtos "first" (see proto-).
eyes...of that baffling protean grey which is never twice the same
prostrate
prostration
prosy
Prot
protagonist
Protean
protease
protect
protectant
protection
protectionism